1. Field of the Invention
The present invention relates to a driving technique for a sensorless fan motor, and particularly to a technique for starting up such a sensorless fan motor.
2. Description of the Related Art
With a sensorless motor, back electromotive force does not occur in the stationary state. Accordingly, in this state, the sensorless driving operation of such a sensorless motor cannot be started up based upon back electromotive force. A technique has been proposed in which the rotor position is detected by means of a position detection function for detecting the position of the rotor, and a logic driving signal that corresponds to the detected position is applied to the sensorless motor so as to supply a suitable torque such that the sensorless motor rotates in the normal direction (e.g., Patent documents 1 and 2).